Fluorescent light fixtures include tubular fluorescent bulbs. A fluorescent bulb is also referred to here as a fluorescent lamp. The tube is a glass tube that contains an ionizable gas and a small amount of mercury. There are filaments at each end of the tube. Upon application of proper electrical voltages, the filaments can be made to heat up and to ionize the ionizable gas in the tube. If a voltage of adequate magnitude is then provided between the filaments, an electrical arc can be started through the gas in the tube between the filaments. The arc involves a flow of current from one filament, through the ionized gas, and to the other filament. Energetic electrons in this current flow collide with the mercury atoms, thereby exciting the mercury atoms and causing them to emit ultraviolet radiation. The emitted ultraviolet radiation is absorbed by and excites a phosphor coating on the inside of the walls of the tube. The phosphor coating fluoresces and emits radiation in the visible spectrum (i.e., visible light). The visible light passes outward through the glass and is usable for illuminating purposes.
Some such fluorescent light fixtures involve a circuit referred to as a “starter” or a “starter unit”. In a first step, a switch in the starter unit closes and forms an electrical connection between the filament at one end of a tube and the filament at the other end of the tube such that an alternating current can flow from an AC power source, through an inductive ballast, through one filament, through the closed switch of the starter, and through the second filament, and back to the AC power source. This alternating current flow causes the filaments to heat. The heating of the filaments causes gas surrounding the filaments to ionize. Once the gas is ionized in this way, then the switch in the starter unit is opened. The opening of the switch cuts current flow through the inductive ballast, thereby causing a large voltage spike to develop. Due to the circuit topology, this large voltage is present between the two filaments. The voltage is large enough to strike an arc through the gas. Once the arc is established, the resistance between the two filaments through the gas decreases. This allows the current to continue to flow through the gas without a large voltage being present between the filaments. The switch is left open, the current continues to flow, filaments continue to be heated, the arc is maintained, and the current flow is regulated by the ballast. The fluorescent lamp is then said to be on. The lamp emits visible light to illuminate an area.
In fluorescent light fixtures, the starter unit may fail. The starter unit is therefore sometimes made to be a replaceable unit. Great numbers of fluorescent light fixtures with replaceable starter units are installed throughout the world. Large numbers of such fluorescent light fixtures are installed in public buildings, office buildings, and other large buildings. Quite often the fluorescent lights are left on and consume electrical energy even though the area served does not need to be illuminated. A way of preventing this waste of electrical energy is desired.
Infrared motion detecting wall switches are often employed to prevent the waste of energy due to lights being left on when lighting is not needed. If an infrared motion detector in the wall switch does not detect motion of an infrared emitter (for example, a human body) in the vicinity of the wall switch, then circuitry in the wall switch determines that the room is not occupied by a person. Presumably if a person were in the room, the person would be moving to some extent and would be detected as a moving infrared emitter. If the wall switch determines that the room is unoccupied because it does not detect any such moving infrared emitter, then the wall switch turns off the fluorescent lights on the circuit controlled by the wall switch. The wall switch turns off the fluorescent lights by cutting AC power flowing to the fluorescent lamp light fixtures through power lines hardwired into the building. If, however, the wall switch detects a moving infrared emitter, then the wall switch turns on the lights by energizing the hardwired power lines so that AC power is supplied to the fluorescent light fixtures through the hardwired power lines.
The wall switch motion detection system involving hardwired power lines embedded in the walls and ceilings of buildings is quite popular, but a wireless system has been proposed whereby each of the replaceable starter units is to be provided with an RF receiver. The starter unit is then to turn on or off the fluorescent lamp of its light fixture in response to RF commands received from a central motion detecting occupancy detector. If a person enters a room provided with such a system, then the central motion detector detects motion and issues RF commands to the starter units in the light fixtures to turn on their respective fluorescent lamps. If the central motion detector fails to detect motion for an amount of time and determines that the room is not occupied, then the central motion detector issues RF commands to the starter units to turn off their respective fluorescent lamps, thereby preventing wasted electrical power that would otherwise be consumed illuminating the unoccupied room.
In a proposed system, different timing is to be employed in a starter unit to turn off a fluorescent lamp depending on the type of ballast being used. There are many types of ballasts used to limit current flow through fluorescent lamps including ballasts referred to here as L-type ballasts and including ballasts referred to here as C-type ballasts. An L-type ballast is generally an inductor whereas a C-type ballast is an inductor that includes a series capacitor. In the proposed system, each starter unit attempts to detect the type of ballast to which it is connected. If the starter unit detects it is connected to an L-type ballast, then it uses turn off timing more appropriate for lamps having L-type ballasts. If the starter unit detects it is connected to a C-type ballast, then it used turn off timing more appropriate for lamps having C-type ballasts. Often times a light fixture employing multiple lamps will include one L-type ballast and one C-type ballast so that the overall power factor of the light fixture is suitable. The starter units in the fixture of the proposed system therefore would use different timings to turn off the lamps. Other times a light fixture employing multiple lamps will include two C-type ballasts, or will include two L-type ballasts. The starter units in these fixtures of the proposed system would use the same timings to turn off the lamps.